Alternating current driven quantum dot electroluminescent device

Abstract

The invention relates to an alternating current driven quantum dot electroluminescent device, and belongs to the technical field of luminescent devices. The device comprises a first tunneling heterojunction layer, a light-emitting layer and a second tunneling heterojunction layer, the first tunneling heterojunction layer comprises a tunneling layer A and a tunneling layer B; the second tunneling heterojunction layer comprises a tunneling layer C, a tunneling layer D and a tunneling layer E; the tunneling layer A and the tunneling layer D are independently made of an n-type conductive polymer material and / or an n-type metal oxide semiconductor material of which the work function is greater than 5.1 eV; the materials of the tunneling layer B and the tunneling layer E are independently p-type materials of which the highest occupied molecular orbital HOMO energy level is between-5.0 eV and-6.0 eV; and the tunneling layer C is made of an n-type electron transport material of which the lowest occupied molecular orbital (LUMO) energy level is-2.5 eV to-4.5 eV. The device provided by the invention effectively solves the problems of device attenuation related to carrier injection, charge injection imbalance relief, overhigh working voltage of the device and insufficient luminous intensity.

Description

Technical Field

[0001] The present invention belongs to the technical field of light-emitting devices, and in particular relates to an alternating current driven quantum dot electroluminescent device. Background Art

[0002] Quantum dot light-emitting diodes (QLEDs) have a wide range of applications in flat panel displays, lighting and other fields. The QLED device structure consists of an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode. Electrons and holes are injected into the light-emitting layer through the cathode and anode, respectively, and emit light through radiation recombination. Typically, QLEDs are charge injection devices that operate under direct current (DC) and low voltage conditions. Although QLEDs have achieved a high external quantum efficiency of light emission, continuous operation with direct current leads to irreversible charge accumulation, which damages the working life of the device.

[0003] AC-driven quantum dot electroluminescent devices can not only effectively avoid charge accumulation in the device through the alternating electric field, but also simplify the driving circuit and reduce the preparation cost of the panel. Therefore, the development of AC-driven quantum dot light-emitting devices is crucial to enriching electroluminescent technology, expanding the application scenarios of quantum dot materials, and developing micro-display technology. For quantum dot display technology, AC field drive is also an ideal way to achieve quantum dot electroluminescence with high stability.

[0004] In order to realize AC-driven quantum dot electroluminescent devices, the existing technologies can be roughly divided into: First, quantum dot light-emitting diodes (QLEDs) are directly used for AC drive: Since QLEDs in DC drive mode are prone to unfavorable charge accumulation on the light-emitting layer, resulting in poor working stability, using AC voltage drive instead of DC drive without changing the QLED structure can avoid charge accumulation inside the device through an alternating electric field and increase the working life of the device; however, the device attenuation mechanism caused by external charge injection still exists, making it difficult to improve device stability. Second, devices with charge injection on one side: AC electroluminescent devices (AC-EL) with a single layer of insulating medium; one side of the electrode can inject carriers into the quantum dot light-emitting layer. There is an insulating material between the other electrode and the quantum dot light-emitting layer to block carrier injection, and carriers are generated by electric field induced ionization; for example, holes (or electrons) are injected from one electrode, electrons (or holes) are ionized by the electric field, and electron-holes form excitons in the quantum dots and radiate recombination to emit light; however, the design of the single-sided insulating layer leads to voltage loss in the dielectric layer and electron-hole imbalance problems, which reduces the luminescence efficiency and stability of the device. The third is the traditional device without charge injection: an alternating current electroluminescent device (AC-EL) with a double-layer insulating medium; there is insulating material between the electrodes on both sides and the quantum dot light-emitting layer to block carrier injection; its luminescence mechanism is that under the action of the alternating electric field, electrons and holes are generated by electric field-induced ionization in the first half cycle of the alternating electric field, and in the second half cycle of the alternating electric field, the electrons-holes form excitons in the quantum dots under the drive of the electric field, and radiate and recombine to emit light, which is completely dependent on the high electric field to ionize the valence electrons in the quantum dots to form electrons and holes that can be used for light emission; on the one hand, the number of carriers is extremely low, which increases the device operating voltage and limits the device's luminescence intensity; on the other hand, the high electric field in the luminescent quantum dot layer can easily lead to exciton quenching in the quantum dots and the quantum confined Stark effect, which significantly reduces the probability of quantum dot radiative recombination and reduces the device's luminescence intensity. Summary of the invention

[0005] To this end, the technical problem to be solved by the present invention is to overcome the problems of device attenuation caused by carrier injection, unbalanced charge injection, excessively high device operating voltage, insufficient luminous intensity, etc. in the AC-driven quantum dot electroluminescent devices in the prior art.

[0006] In order to solve the above technical problems, the present invention provides an AC driven quantum dot electroluminescent device.

[0007] The object of the present invention is to provide an AC-driven quantum dot electroluminescent device, which comprises, from bottom to top, a first electrode, a first dielectric layer, a first tunneling heterojunction layer, a light-emitting layer, a second tunneling heterojunction layer, a second dielectric layer, and a second electrode, which are arranged in sequence; the first tunneling heterojunction layer comprises a tunneling layer A and a tunneling layer B; the second tunneling heterojunction layer comprises a tunneling layer C, a tunneling layer D, and a tunneling layer E;

[0008] The materials of the tunneling layer A and the tunneling layer D are independently selected from n-type conductive polymer materials and / or n-type metal oxide semiconductor materials having a work function greater than 5.1 eV.

[0009] The materials of the tunneling layer B and the tunneling layer E are independently selected from p-type polymer semiconductor materials with the highest occupied molecular orbital HOMO energy level between -5.0 eV and -6.0 eV;

[0010] The material of the tunneling layer C is selected from n-type electron transport materials with a lowest occupied molecular orbital LUMO energy level of -2.5 eV to -4.5 eV.

[0011] In one embodiment of the present invention, the n-type conductive polymer material is selected from One or more of OC, PEDOT:PSS, PEDOT-PFESA, PTT:PFFSA, phosphomolybdic acid (PMA), and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanodimethyl-p-benzoquinone (F4TCNQ).

[0012] In one embodiment of the present invention, the n-type metal oxide semiconductor material is selected from one or more of molybdenum oxide, vanadium pentoxide, tungsten oxide and nickel oxide.

[0013] In one embodiment of the present invention, the p-type polymer semiconductor material with the highest occupied molecular orbital HOMO energy level between -5.0 eV and -6.0 eV is selected from one or more of poly [(N,N'-(4-n-butylphenyl)-N,N'-diphenyl-1,4-phenylenediamine)-ALT-(9,9-di-n-octylfluorenyl-2,7-diyl)] (TFB), poly (9-vinylcarbazole) (PVK), poly [bis (4-phenyl) (4-butylphenyl) amine] (Poly-TPD) and poly trihexanethiophene (P3HT); the p-type polymer semiconductor material has good film forming properties and hole mobility.

[0014] In one embodiment of the present invention, the n-type electron transport material is selected from zinc oxide (ZnO), tin dioxide (SnO2), zinc magnesium oxide (Zn 1-x Mg xO) and 5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) one or more; the n-type electron transport material has good electron mobility.

[0015] In one embodiment of the present invention, the thickness of the tunneling layer A is 5nm-30nm; the thickness of the tunneling layer B is 10nm-50nm; the thickness of the tunneling layer C is 10nm-50nm; the thickness of the tunneling layer D is 5nm-30nm; and the thickness of the tunneling layer E is 10nm-50nm.

[0016] In one embodiment of the present invention, the material of the light-emitting layer is selected from one or more of II-VI quantum dot (nanocrystalline) materials, III-V quantum dot (nanocrystalline) materials, perovskite quantum dot materials and organic light-emitting materials.

[0017] Furthermore, the II-VI quantum dot (nanocrystalline) material is one or more of cadmium-based quantum dots (cadmium selenide, cadmium sulfide), zinc-based quantum dots (zinc selenide, zinc telluride), and zinc-cadmium-based alloy quantum dots (ZnCdSeS).

[0018] Furthermore, the III-V quantum dot (nanocrystalline) material is an indium-based quantum dot (indium phosphide, indium arsenide)

[0019] Furthermore, the perovskite quantum dot material is a quantum dot material or bulk material such as cesium bromide, cesium bromide-chloride, methylamine bromide, and methylammonium iodide.

[0020] Furthermore, the organic light-emitting material is a fluorescent material, a phosphorescent material, a thermally activated delayed fluorescent material, such as an aromatic pyridine type, an imidazole type, a pyrimidine type, a carbene type, an arylquinoline type, a 2,3-diphenylquinoxaline (DPQ) derivative, an aromatic carbonyl, a heavy atom or / and a heterocyclic / heteroatom-containing compound, a sulfonodiphenyl type, a cyano type, a triazine type, an aromatic ketone type, a sulfone derivative, anthraquinone type, a 2,1,3-benzothiadiazole type, and a 2,3-dicyanopyrazine and anthracene material.

[0021] Furthermore, the thickness of the light-emitting layer is 20nm-200nm.

[0022] In one embodiment of the present invention, the materials of the first dielectric layer and the second dielectric layer are independently selected from one or more of aluminum oxide (Al2O3), silicon dioxide (SiO2), hafnium dioxide (HfO2), zirconium dioxide (ZrO2), niobium pentoxide (Nb2O5), silicon carbide (SiC), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-trifluoroethylene) copolymer (P(VDF-TrFE)), n-octadecylphosphonic acid (ODPA) and n-octadecyltrichlorosilane (ODTS).

[0023] Furthermore, the thickness of the first dielectric layer and the second dielectric layer are independently 50 nm-300 nm.

[0024] In one embodiment of the present invention, materials of the first electrode and the second electrode are independently selected from one or more of indium tin oxide (ITO), fluorine-doped tin dioxide (FTO), aluminum (Al) and silver (Ag).

[0025] Furthermore, the thickness of the first electrode and the second electrode are independently 10 nm-300 nm.

[0026] In one embodiment of the present invention, the AC-driven quantum dot electroluminescent device further comprises a substrate.

[0027] In one embodiment of the present invention, the material of the substrate is selected from one or more of glass, polyethylene terephthalate (PET) and polyimide (PI).

[0028] The technical solution of the present invention has the following advantages over the prior art:

[0029] (1) The quantum dot electroluminescent device described in the present invention has a tunneling heterojunction on each side. The first tunneling heterojunction is composed of two thin films, namely, tunneling layer A and tunneling layer B. In a half-cycle, electrons are generated in tunneling layer A, holes are generated in tunneling layer B, and holes are injected into the light-emitting quantum dots of the light-emitting layer. The second tunneling heterojunction is composed of three thin films, namely, tunneling layer C, tunneling layer D, and tunneling layer E. On the one hand, in a half-cycle, electrons are generated in tunneling layer D under the action of an electric field, and holes are generated in tunneling layer E. On the other hand, the high work function of tunneling layer D causes a significant vacuum energy level shift at the interface between the two after contacting tunneling layer C, so that tunneling layer C and tunneling layer D form energy level matching, thereby successfully injecting electrons generated in tunneling layer D into the light-emitting quantum dots of the light-emitting layer through an n-type electron injection material in a positive half-cycle. The holes injected from tunneling layer B and the electrons injected from tunneling layer C form excitons in the light-emitting quantum dots of the light-emitting layer and emit light.

[0030] (2) In the quantum dot electroluminescent device described in the present invention, during the AC driving half-cycle when the device does not emit light, the electric field extracts the charge in the quantum dots and causes them to recombine in the tunneling heterojunction, which is beneficial to reducing the quantum dot electroluminescent attenuation and improving the stability of the device. The first tunneling heterojunction and the second tunneling heterojunction serve as carrier production units to provide holes and electrons to the light-emitting layer respectively, and maintain charge balance, which can significantly increase the luminous intensity of the device. The depletion regions of the first tunneling heterojunction and the second tunneling heterojunction bear most of the electric field, thereby reducing the electric field intensity in the quantum dot layer, alleviating field-induced quenching and quantum confined Stark effect, and reducing the operating voltage.

[0031] (3) The quantum dot electroluminescent device described in the present invention effectively solves the device attenuation problem related to carrier injection, alleviates the problem of charge injection imbalance, and solves the problem of excessively high device operating voltage and insufficient luminous intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0033] Figure 1 It is a schematic diagram of the structure of the quantum dot electroluminescent device of the present invention;

[0034] Figure 2 Schematic diagram of the molecular structure of the tunneling layer D material PMA of the present invention;

[0035] Figure 3 A comparison diagram of brightness-voltage test curves of devices prepared in Example 1 of the present invention and in Comparative Example 1;

[0036] Figure 4 A comparison diagram of brightness-voltage test curves of devices prepared in Example 2 of the present invention and Comparative Example 2;

[0037] Figure 5 A comparison diagram of brightness-voltage test curves of devices prepared in Example 3 of the present invention and Comparative Example 3;

[0038] Figure 6 The electroabsorption of the light-emitting layer of the device prepared in Example 1 of the present invention and Comparative Example 1 is -V AC 2 Comparison chart;

[0039] Figure 7 The electroabsorption of the light-emitting layer of the device prepared in Example 2 of the present invention and Comparative Example 2 is -V AC 2 Comparison chart;

[0040] Figure 8 The electroabsorption of the light-emitting layer of the device prepared in Example 3 of the present invention and Comparative Example 3 is -V AC 2 Comparison chart;

[0041] Explanation of the accompanying drawings: 1-substrate, 2-first electrode, 3-first dielectric layer, 4-first tunneling heterojunction layer, 41-tunneling layer A, 42-tunneling layer B, 5-light-emitting layer, 6-second tunneling heterojunction layer, 61-tunneling layer C, 62-tunneling layer D, 63-tunneling layer E, 7-second dielectric layer, 8-second electrode. DETAILED DESCRIPTION

[0042] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0043] The above and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of the embodiments with reference to the accompanying drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front or back, etc., are only the directions with reference to the accompanying drawings. Therefore, the directional terms used are used to illustrate and not to limit the present invention. In addition, in all embodiments, the same reference numerals represent the same elements.

[0044] In the present invention, unless otherwise specified, the ITO substrate used in the embodiments is an ITO conductive glass, including a glass substrate 1 and an ITO first electrode 2 .

[0045] In the present invention, unless otherwise specified, the lowest occupied molecular orbital LUMO energy level of the material of the tunneling layer C in the embodiment matches that of the tunneling layer D;

[0046] In the present invention, unless otherwise specified, the OC was purchased from Merck. The work function of OC is 5.5 eV.

[0047] In the present invention, unless otherwise specified, the work function of molybdenum oxide (MoO3) used in the examples is 6.9 eV.

[0048] In the present invention, unless otherwise specified, the work function of phosphomolybdic acid (PMA) used in the examples is 6.4 eV.

[0049] In the present invention, unless otherwise specified, the HOMO level of TFB used in the examples is -5.4 eV.

[0050] In the present invention, unless otherwise specified, the HOMO level of Poly-TPD used in the examples is -5.2 eV.

[0051] In the present invention, unless otherwise specified, the LUMO energy level of ZnO used in the examples is -3.87 eV.

[0052] In the present invention, unless otherwise specified, the LUMO energy level of SnO2 used in the examples is -3.42 eV.

[0053] In the present invention, unless otherwise specified, the LUMO energy level of TPBi used in the examples is -2.7 eV.

[0054] Reference Figure 1As shown, the quantum dot electroluminescent device and the preparation method thereof of the present invention specifically include the following steps: using cadmium-based quantum dots (Cd-QDs) with an emission wavelength of 470nm as the light-emitting layer.

[0055] (1) The ITO substrate was ultrasonically cleaned with glass cleaning solution, deionized water, acetone, and isopropanol for 30 minutes, and then dried and treated in ultraviolet ozone for 15 minutes.

[0056] (2) The ITO substrate is transferred to a sputtering chamber, and a first dielectric layer 3 is deposited by magnetron sputtering at a radio frequency power of 150 W and an argon (Ar) gas: oxygen (O2) ratio of 10:1 to form a SiO2 film with a thickness of about 100 nm.

[0057] (3) Preparation of the first tunneling heterojunction layer 4: After the substrate is taken out of the sputtering chamber, it is moved to the evaporation chamber to evaporate the tunneling layer A41 to form a MoO3 film with a thickness of about 10 nm; then, the tunneling layer B 42 is spin-coated in a nitrogen glove box and annealed at 150°C for 30 min to form a TFB film with a thickness of about 30 nm.

[0058] (4) The light-emitting layer was prepared by spin coating at a rotation speed of 2000 rpm to form a cadmium-based quantum dot (Cd-QDs) film with a thickness of about 25 nm.

[0059] (5) Preparation of the second tunneling heterojunction layer 6: spin coating the tunneling layer C 61 to form a zinc oxide nanoparticle (ZnO) film with a thickness of about 35 nm; after the substrate is cooled, spin coating the tunneling layer D 62, heating and annealing at 150° C. to form a phosphomolybdic acid (PMA, structure as shown in FIG. 1 ) film with a thickness of about 10 nm. Figure 2 and then spin-coating the tunneling layer E 63 at a rotation speed of 3000 rpm, heating and annealing at 120° C. to form a TFB film with a thickness of about 30 nm.

[0060] (6) The second dielectric layer 7 is sputtered by magnetron sputtering under the reaction conditions of RF power of 150 W and argon (Ar): oxygen (O2) of 10:1 to form a SiO2 film with a thickness of about 100 nm.

[0061] (7) The second electrode 8 is deposited in a vacuum thermal evaporation device to form an Ag film with a thickness of about 100 nm; the completed device structure is: ITO / SiO2 / MoO3 / TFB / Cd-QDs / ZnO / PMA / TFB / SiO2 / Ag.

[0062] Example 2

[0063] The quantum dot electroluminescent device and the preparation method thereof of the present invention specifically include the following steps: using indium phosphide quantum dots (InP-QDs) with an emission wavelength of 620nm as a light-emitting layer.

[0064] (1) The glass substrate 1 was ultrasonically cleaned for 30 minutes using glass cleaning liquid, deionized water, acetone, and isopropanol, respectively, and then placed in ultraviolet ozone for 15 minutes after drying; the glass substrate was transferred to a vapor deposition chamber to deposit a first electrode 2 to form a Ag film with a thickness of about 100 nm.

[0065] (2) The first dielectric layer 3 is deposited by magnetron sputtering under the reaction conditions of RF power of 120 W and argon (Ar): oxygen (O2) of 10:1 to form an Al2O3 film with a thickness of about 100 nm.

[0066] (3) Preparation of the first tunneling heterojunction layer 4: After the substrate is taken out of the sputtering chamber, it is moved to the evaporation chamber to evaporate the tunneling layer A41 to form a MoO3 film with a thickness of about 10 nm; then, the tunneling layer B 42 is spin-coated in a nitrogen glove box and annealed at 150°C for 30 min to form a TFB film with a thickness of about 30 nm.

[0067] (4) The light-emitting layer was prepared by spin coating at a rotation speed of 2000 rpm to form an indium phosphide quantum dot (InP-QDs) film with a thickness of about 35 nm.

[0068] (5) Preparation of the second tunneling heterojunction layer 6: spin coating the tunneling layer C 61 to form a tin oxide nanoparticle (SnO2) film with a thickness of about 40 nm; after the substrate is cooled, spin coating the tunneling layer D 62, heating and annealing at 150° C. to form a phosphomolybdic acid (PMA) film with a thickness of about 10 nm; then spin coating the tunneling layer E 63 at a rotation speed of 3000 rpm, heating and annealing at 120° C. to form a TFB film with a thickness of about 30 nm.

[0069] (6) The second dielectric layer 7 is sputtered by magnetron sputtering at a radio frequency power of 120 W and an argon (Ar) gas: oxygen (O2) ratio of 10:1 to form an Al2O3 film with a thickness of about 100 nm.

[0070] (7) The second electrode 8 is deposited by magnetron sputtering to form an ITO film with a thickness of about 150 nm; the completed device structure is: Ag / Al2O3 / MoO3 / TFB / InP-QDs / SnO2 / PMA / TFB / Al2O3 / ITO.

[0071] Example 3

[0072] The quantum dot electroluminescent device and the preparation method thereof of the present invention specifically include the following steps: using perovskite quantum dots (PeQDs) with an emission wavelength of 536 nm as a light-emitting layer.

[0073] (1) The ITO substrate was ultrasonically cleaned with glass cleaning solution, deionized water, acetone, and isopropanol for 30 minutes, and then dried and treated in ultraviolet ozone for 15 minutes.

[0074] (2) The ITO substrate is transferred to a sputtering chamber, and a first dielectric layer 3 is deposited by magnetron sputtering under the reaction conditions of 120 W radio frequency power and argon (Ar): oxygen (O2) of 10:1 to form an Al2O3 film with a thickness of about 100 nm.

[0075] (3) Preparation of the first tunneling heterojunction layer 4: After the substrate is taken out of the sputtering chamber, a tunneling layer A41 is spin-coated at a speed of 4000 rpm using a coater in a nitrogen glove box, and then heated and annealed at 170° C. to form a film with a thickness of about 30 nm. OC film; after the substrate is cooled, the tunneling layer B 42 is spin-coated at a speed of 8000 rpm in a nitrogen glove box, and annealed at 150° C. for 30 min to form a Poly-TPD film with a thickness of about 30 nm.

[0076] (4) The light-emitting layer was prepared by spin coating at a rotation speed of 2000 rpm to form a perovskite quantum dot (PeQDs) film with a thickness of about 30 nm.

[0077] (5) Preparation of the second tunneling heterojunction layer 6: Tunneling layer C 61 and tunneling layer D 62 are sequentially deposited in a vacuum thermal evaporation device to form a TPBi film with a thickness of about 30 nm and a MoO3 film with a thickness of about 10 nm; then, a high molecular weight tunneling layer E 63 is spin-coated at a rotation speed of 8000 rpm in a nitrogen glove box, and after heating and annealing at 150° C., a Poly-TPD film with a thickness of about 30 nm is formed.

[0078] (6) The second dielectric layer 7 is sputtered and deposited by magnetron sputtering at a radio frequency power of 120 W and an argon (Ar) gas: oxygen (O2) ratio of 10:1 to form an Al2O3 film with a thickness of about 100 nm.

[0079] (7) Depositing the second electrode 8 in a vacuum thermal evaporation device to form an Al film with a thickness of about 100 nm; the completed device structure is: ITO / Al2O3 / OC / Poly-TPD / PeQDs / TPBi / MoO3 / Poly-TPD / Al2O3 / Al.

[0080] Comparative Example 1 is basically the same as Example 1, except that: the first tunneling heterojunction layer 4 and the second tunneling heterojunction layer 6 are not provided.

[0081] Cadmium-based quantum dots (Cd-QDs) with an emission wavelength of 470 nm are used as the light-emitting layer.

[0082] (1) The ITO substrate was ultrasonically cleaned with glass cleaning solution, deionized water, acetone, and isopropanol for 30 minutes, and then dried and treated in ultraviolet ozone for 15 minutes.

[0083] (2) The ITO substrate is transferred to a sputtering chamber, and a first dielectric layer 3 is deposited by magnetron sputtering at a radio frequency power of 150 W and an argon (Ar) gas: oxygen (O2) ratio of 10:1 to form a SiO2 film with a thickness of about 100 nm.

[0084] (3) The light-emitting layer was prepared by spin coating at a rotation speed of 2000 rpm in a nitrogen glove box to form a cadmium-based quantum dot (Cd-QDs) film with a thickness of about 25 nm.

[0085] (4) The second dielectric layer 7 is sputtered by magnetron sputtering under the reaction conditions of RF power of 150 W and argon (Ar): oxygen (O2) of 10:1 to form a SiO2 film with a thickness of about 100 nm.

[0086] (5) The second electrode 8 is deposited in a vacuum thermal evaporation device to form an Ag film with a thickness of about 100 nm; the completed device structure is: ITO / SiO2 / Cd-QDs / SiO2 / Ag.

[0087] Comparative Example 2 is basically the same as Example 2, except that: the first tunneling heterojunction layer 4 is not provided.

[0088] Indium phosphide quantum dots (InP-QDs) with an emission wavelength of 620 nm are used as the light-emitting layer.

[0089] (1) The glass substrate was ultrasonically cleaned for 30 minutes using glass cleaning solution, deionized water, acetone, and isopropanol, respectively, and then placed in ultraviolet ozone for 15 minutes after drying; the glass substrate was transferred to a vapor deposition chamber to deposit a first electrode 2 to form a Ag film with a thickness of about 100 nm.

[0090] (2) The first dielectric layer 3 is deposited by magnetron sputtering under the reaction conditions of RF power of 120 W and argon (Ar): oxygen (O2) of 10:1 to form an Al2O3 film with a thickness of about 100 nm.

[0091] (3) Then, the light-emitting layer was prepared by spin coating at a rotation speed of 2000 rpm in a nitrogen glove box to form an indium phosphide quantum dot (InP-QDs) film with a thickness of about 35 nm.

[0092] (4) Preparation of the second tunneling heterojunction layer 6: spin coating the tunneling layer C 61 to form a tin oxide nanoparticle (SnO2) film with a thickness of about 40 nm; after the substrate is cooled, spin coating the tunneling layer D 62, heating and annealing at 150° C. to form a phosphomolybdic acid (PMA) film with a thickness of about 10 nm; then spin coating the tunneling layer E 63 at a rotation speed of 3000 rpm, heating and annealing at 120° C. to form a TFB film with a thickness of about 30 nm.

[0093] (5) The second dielectric layer 7 is sputtered by magnetron sputtering at a radio frequency power of 120 W and an argon (Ar) to oxygen (O2) ratio of 10:1 to form an Al2O3 film with a thickness of about 100 nm.

[0094] (6) The second electrode 8 is deposited by magnetron sputtering to form an ITO film with a thickness of about 150 nm; the completed device structure is: Ag / Al2O3 / InP-QDs / SnO2 / PMA / TFB / Al2O3 / ITO.

[0095] Comparative Example 3 is basically the same as Example 3, except that the second tunneling heterojunction layer 6 is not provided.

[0096] Perovskite quantum dots (PeQDs) with an emission wavelength of 536 nm are used as the light-emitting layer.

[0097] (1) The ITO substrate was ultrasonically cleaned with glass cleaning solution, deionized water, acetone, and isopropanol for 30 minutes, and then dried and treated in ultraviolet ozone for 15 minutes.

[0098] (2) The ITO substrate is transferred to a sputtering chamber, and a first dielectric layer 3 is deposited by magnetron sputtering under the reaction conditions of 120 W radio frequency power and argon (Ar): oxygen (O2) of 10:1 to form an Al2O3 film with a thickness of about 100 nm.

[0099] (3) Preparation of the first tunneling heterojunction layer 4: After the substrate is taken out of the sputtering chamber, a tunneling layer A41 is spin-coated at a speed of 4000 rpm using a coater in a nitrogen glove box, and then heated and annealed at 170° C. to form a film with a thickness of about 30 nm. OC film; after the substrate is cooled, the tunneling layer B 42 is spin-coated at a speed of 8000 rpm in a nitrogen glove box, and annealed at 150° C. for 30 min to form a Poly-TPD film with a thickness of about 30 nm.

[0100] (4) In a nitrogen glove box, a light-emitting layer was prepared by spin coating at a rotation speed of 2000 rpm to form a perovskite quantum dot (PeQDs) film with a thickness of about 30 nm.

[0101] (5) The second dielectric layer 7 is sputtered and deposited by magnetron sputtering at a radio frequency power of 120 W and an argon (Ar) to oxygen (O2) ratio of 10:1 to form an Al2O3 film with a thickness of about 100 nm.

[0102] (6) Depositing the second electrode 8 in a vacuum thermal evaporation device to form an Al film with a thickness of about 100 nm; the completed device structure is: ITO / Al2O3 / OC / Poly-TPD / PeQDs / Al2O3 / Al.

[0103] Test Example 1

[0104] The devices in Examples 1-3 and Comparative Examples 1-3 were respectively subjected to an AC electric field, and the brightness of the devices under fixed driving conditions was measured using a brightness meter, a voltage amplifier, and a function generator. The results are as follows: Figure 3-5 As shown. Figure 3 It can be seen that compared with Comparative Example 1, the brightness of the device in Example 1 is significantly improved and the operating voltage is significantly reduced, which indicates that the number of carriers in Example 1 is significantly improved. Figure 4 It can be seen that when the frequency is 250kHz and the peak-to-peak value is 90V pp When the device is driven by an alternating voltage, the brightness of the device in Example 2 is significantly increased to 1500 cd / m 2 , which indicates that the number of carriers in Example 2 is significantly increased. Figure 5 It can be seen that the brightness of the device in Example 3 is greatly improved compared with that in Comparative Example 3. This indicates that compared with the comparative example, the first tunneling heterojunction and the second tunneling heterojunction of the device in the embodiment provide holes and electrons to the light-emitting layer as carrier production units, respectively, thereby increasing the number of carriers and leading to an increase in the luminescence intensity of the device. In addition, under the same AC driving conditions, the intensity of the electroabsorption signal is used to estimate the degree of reduction in the operating voltage of the QD layer in the structure.

[0105] Test Example 2

[0106] Based on Test Example 1, the devices in Examples 1-3 and Comparative Examples 1-3 were tested under the same AC driving conditions using a monochromator, current amplifier, lock-in amplifier, function generator, voltage amplifier and other main instruments to build an electro-absorption test platform based on phase-locked noise reduction technology. The electro-absorption signal intensity of the device was measured to analyze the degree of reduction in the working voltage of the QD layer in the structure. The results are as follows: Figure 6-8 As shown. Figure 6-8 It can be seen that since the signal intensity of electroabsorption in the second harmonic measurement mode is linearly proportional to the square of the average electric field in the quantum dot, by comparing the electroabsorption signal intensity, it can be seen that under the same driving conditions, the signal intensity of the embodiment device is significantly lower than that of the comparative device, with an average reduction of 32.45%, 30.82%, and 34.8%, respectively. The reduction comes from the sharing of the electric field by the depletion regions of the first tunneling heterojunction and the second tunneling heterojunction. This shows that the embodiment can reduce the electric field intensity in the quantum dot layer to a greater extent than the comparative example, which significantly improves the radiation recombination probability of the quantum dots.

[0107] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. An AC-driven quantum dot electroluminescent device, characterized in that: From bottom to top, it includes a first electrode, a first dielectric layer, a first tunneling heterojunction layer, a light-emitting layer, a second tunneling heterojunction layer, a second dielectric layer, and a second electrode arranged in sequence; the first tunneling heterojunction layer includes a tunneling layer A and a tunneling layer B; the second tunneling heterojunction layer includes a tunneling layer C, a tunneling layer D, and a tunneling layer E; The materials of the tunneling layer A and the tunneling layer D are independently selected from n-type conductive polymer materials and / or n-type metal oxide semiconductor materials having a work function greater than 5.1 eV; The materials of the tunneling layer B and the tunneling layer E are independently selected from p-type polymer semiconductor materials with the highest occupied molecular orbital HOMO energy level between -5.0 eV and -6.0 eV; The material of the tunneling layer C is selected from n-type electron transport materials with a lowest occupied molecular orbital LUMO energy level of -2.5 eV to -4.5 eV.

2. The AC-driven quantum dot electroluminescent device according to claim 1, characterized in that: The n-type conductive polymer material is selected from One or more of OC, PEDOT:PSS, PEDOT-PFESA, PTT:PFFSA, phosphomolybdic acid, and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanodimethyl-p-benzoquinone.

3. The AC-driven quantum dot electroluminescent device according to claim 1, characterized in that: The n-type metal oxide semiconductor material is selected from one or more of molybdenum oxide, vanadium pentoxide, tungsten oxide and nickel oxide.

4. The AC-driven quantum dot electroluminescent device according to claim 1, characterized in that: The p-type polymer semiconductor material having the highest occupied molecular orbital HOMO energy level between -5.0 eV and -6.0 eV is selected from one or more of poly[(N,N'-(4-n-butylphenyl)-N,N'-diphenyl-1,4-phenylenediamine)-ALT-(9,9-di-n-octylfluorenyl-2,7-diyl)], poly(9-vinylcarbazole), poly[bis(4-phenyl)(4-butylphenyl)amine] and polytrihexanethiophene.

5. The AC-driven quantum dot electroluminescent device according to claim 1, characterized in that: The n-type electron transport material is selected from one or more of zinc oxide, tin dioxide, zinc magnesium oxide and 5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene.

6. The AC-driven quantum dot electroluminescent device according to claim 1, characterized in that: The thickness of the tunneling layer A is 5nm-30nm; the thickness of the tunneling layer B is 10nm-50nm; the thickness of the tunneling layer C is 10nm-50nm; the thickness of the tunneling layer D is 5nm-30nm; and the thickness of the tunneling layer E is 10nm-50nm.

7. The AC-driven quantum dot electroluminescent device according to claim 1, characterized in that: The material of the light-emitting layer is selected from one or more of II-VI quantum dot materials, III-V quantum dot materials, perovskite quantum dot materials and organic light-emitting materials.

8. The AC-driven quantum dot electroluminescent device according to claim 1, characterized in that: The materials of the first dielectric layer and the second dielectric layer are independently selected from one or more of aluminum oxide, silicon dioxide, hafnium dioxide, zirconium dioxide, niobium pentoxide, silicon carbide, polyvinyl alcohol, polyvinylidene fluoride, poly(vinylidene fluoride-trifluoroethylene) copolymer, n-octadecylphosphonic acid and n-octadecyltrichlorosilane.

9. The AC-driven quantum dot electroluminescent device according to claim 1, characterized in that: The materials of the first electrode and the second electrode are independently selected from one or more of indium tin oxide, fluorine-doped tin dioxide, aluminum and silver.

10. The AC-driven quantum dot electroluminescent device according to claim 1, characterized in that: The AC-driven quantum dot electroluminescent device also includes a substrate.

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